The MAC drop-down box contains all the Network Interface Cards (NIC) available to your computer. To test with a network connection on a different NIC when testing to LAN Speed Test Server, just pick a new NIC using this MAC drop-down until the IP address matches the network that you want to test from.
Also, you may have a network connection available to your computer through a wired and wireless interface. Make sure that you have the correct MAC address selected so you are testing with the desired connection.
* When testing to a shared folder, it does not matter which NIC is selected. Your Operating System will automatically choose the best connection to run the test. We can only choose which NIC to test with when testing to LAN Speed Test Server.